How do I reduce tesselation effect with textures?
It's in the creation and size of the texture that determines the quality of "tiling" over large objects. There are many ways to create a texture. You seem to be interested in photographic textures. The key to success here is to have flat even lighting and a camera that is perpendicular to the subject. If you want to optimize the result the camera should be stationary (IE a tripod). High resolution is also important in the original capture.

In the texture itself, for 3D rendering, the “Power of Two” is important. One potential reference http://www.katsbits.com/tutorials/textures/make-better-textures-correct-size-and-power-of-two.php there are many others. The Blender default is 1024 x 1024. I use 2048 x 2048. I believe larger file sizes (in the current environment) offer little advantage and can even slow the system down. There can always be exceptions.

*Depending on the pattern of the original image capture/texture some modification most likely will be necessary to facilitate tiling. Every image/ texture is different but here are some bullet points to follow in creating tillable textures (assuming the above).


Remove from the original image capture any “stand out” features (Like a large blemish on a slab of concrete or maybe a knot in tree bark).
Duplicate the image and scale the height -100% and the erase/delete part of the top or bottom. Flatten.
Repeat the previous for the width.
Use the new texture and make adjustments if necessary.


*The use/knowledge of image editors like Photoshop/Gimp is key here.  But this is not the forum for me go into that level of detail. Hope this was of some help. Maybe I should do a tutorial?